The present invention relates to a side airbag apparatus that protects an occupant of a vehicle from a side impact received by the vehicle.
A side airbag apparatus having an inflator and an airbag is broadly known as an apparatus for protecting an occupant of a vehicle from a side impact applied to the vehicle in a side collision. The airbag is formed by laying an inner fabric portion and an outer fabric portion on top of each other in the widthwise direction of the vehicle and joining the fabric portions together in a bag-like shape. The inflator is arranged in a rear end portion of the interior of the airbag. The airbag, together with the inflator, is incorporated in the back of a seat of the vehicle in a compactly folded state. When a side impact is applied to a side portion of the body of the vehicle, such as a side door, the inflator of the side airbag apparatus supplies inflation gas into the airbag. The inflation gas inflates and deploys the airbag in the forward direction of the vehicle out from the seat back in the narrow space between the occupant seated on the vehicle seat and the body side portion. This attenuates the side impact transmitted to the occupant through the body side portion.
It is known that the lumbar region of the human body generally has superior impact resistance to that of the thorax or the abdomen. However, when the airbag of the aforementioned side airbag apparatus is inflated and deployed, there may be cases in which the airbag presses the corresponding arm of the occupant inward in the widthwise direction of the vehicle. In this case, the thorax or the abdomen of the occupant, which has inferior impact resistance, may receive pressure from the arm.
To solve this problem, Japanese Laid-Open Patent Publication No. 2005-53465, for example, discloses a side airbag apparatus having a looped pressure reducing portion for reducing pressure applied by the arm of the occupant, which portion is arranged in a part of the airbag corresponding to the arm of the occupant. The pressure reducing portion is formed by joining the inner fabric portion and the outer fabric portion with each other at a position corresponding to the arm of the occupant. The side airbag apparatus with the pressure reducing portion limits the thickness of the part of the airbag in which the pressure reducing portion is located in the widthwise direction of the vehicle. This prevents the airbag from pressing the arm of the occupant inward in the widthwise direction of the vehicle and applying pressure onto the thorax or the abdomen.
However, if the arm of the occupant is located offset downward from the pressure reducing portion of the side airbag apparatus before the airbag is inflated and deployed, the following problem will occur. Specifically, when the airbag is inflated and deployed, the portion of the airbag located below the pressure reducing portion, that is, a portion that has a greater thickness in the widthwise direction of the vehicle than the pressure reducing portion, may press the arm of the occupant inward in the widthwise direction of the vehicle. As a result, the intended effect of the pressure reducing portion to prevent the arm of the occupant from applying pressure onto the thorax or the abdomen may not be brought about sufficiently.
To avoid this problem, the area of the pressure reducing portion may be enlarged. However, since an area (a protection area) with a sufficiently great thickness must be ensured in the airbag, the area of the pressure reducing portion can be enlarged only to a limited extent.